Heat can damage sensitive electronic components, degrading reliability and hampering the ability to concentrate higher power levels into smaller packages. Many applications would benefit from the ability to closely package LEDs into compact configurations, but the heat levels generated have always been a limiting factor. As LEDs become more sophisticated, eliminating internal heat build-up has also become increasingly difficult. Devices are becoming more powerful and creating solutions for removing the resulting heat generation often pose great challenges. The drive current through an LED must be controlled. High current densities within the junction of the chip cause partial overheating which damages the crystalline structure of the LED die. At these areas are so called dark line defects, where light ceases to be generated. By rapidly transporting heat away from the junction, dark line defect generation can be reduced or eliminated.
U.S. Patent Publication No. 2003/0036031 to Lieb et al. discloses a light-emitting handpiece for curing light-curable dental resins and similar materials. The device includes a head portion for supporting a LED light source, a tubular handle portion for containing a power source for energizing the LED light source and a nook portion that interconnects the head and handle portions. The head and the neck portions are integrally formed from a common, thermally conductive material and operate to provide a heat sink for the LED. A substantial portion of the light source housing itself functions to dissipate sufficient thermal energy away from the LED allowing the LED to be operated for a time interval sufficient to effect rosin curing.
In U.S. Patent Publication No. 2003/00213 to Herold et al, there is disclosed a method and apparatus for cooling electronic or opto-electronic devices. The apparatus includes the device mounted on a heat sink assembly within a can having a can body and a can header thermally coupled to the heat sink assembly and closing the can body and a thermal conductor outside the can and having a first portion attached to at least part of an edge of the can header and a second portion attached to a thermal sink outside the can.
In U.S. Pat. No. 6,159,005 to Herold et al., there is disclosed a small, light-weight handy device for photo polymerizing synthetic materials. The device includes a built-in battery, a light source constituted by an LED which emits a small useful spectral range only, thereby avoiding any heat radiation. The LED is preferably located at the tip of the device directed towards the site to be polymerized.
In U.S. Pat. No. 6,523,959 to Lu et al., there is disclosed a cooling device to cool a liquid crystal panel and polarizer of an optical system in a liquid crystal projector. The cooling device includes a heat dissipation system comprising a plurality of heat pipes disposed at the two flank sides of said liquid crystal panel.
In U.S. Pat. No. 6,113,212 to Ng et al., there is disclosed a method and apparatus for thermal control of LED print heads using heat pipes to transfer the heat from the LEDs to a heat sink. In this apparatus the LEDs are emitting in a direction that is perpendicular to the axis of the vapor cavity (within the heat pipe) and the LEDs are shown to be mounted, not at the very tip of the heat pipe, but some distance back from the tip mounted on a heat sink as well.
It is believed that none of these U.S. patent documents disclose LEDs on the tips of heat pipes and cooling in a manner to dissipate internal heat energy and packaging the same to achieve maximum light output. A need exists for cooling the LEDs and mounting the same on the heat pipes in a manner which greatly surpasses the performance of conventional cooling techniques and benefit high density, miniaturized LED components. Furthermore, there is a need for a novel LED packaging technology that channels heat away via state-of-the-art micro heat pipes that perform far more efficiently, and in much more compact space, than conventional heat sink technology. Use of heat pipe and LED configurations claimed in this patent application allows the heat to be transported down the heat pipe in an axial direction away from the direction of light propagation. This is in contrast to conventional heat spreaders or heatsinks which transports heat from the die in a radial direction away from it. This prevents close spacing of LED components due to the high thermal energy in a confined area.